3 - Skin glands Flashcards
What are the 2 basic types of skin glands?
Sebaceous glands and sweat glands
What are skin glands modifications of?
The epidermis
What ae sebaceous glands associated with?
Hair follicles
What is the basic structure of a sebaceous gland?
Many lobed (acinar) structure
What do sebaceous glands produce?
Fatty/oily sebum
What is the function of sebum?
- To moisturise and waterproof hair and skin (because it opens to the hair follcile and is distributed over hair and skin)
- allows sweat to spread (thermoregulation)
- Antimicrobial function
- May have pheromones or other scented compounds for communication (it is spread over the hair so diffuses a wiser surface area).
What is sebum called in sheep?
lanolin
What species have circumoral glands?
What are they for?
Where are they located?
Cats
Scent marking and greeting
Around the lips
What species have carpal glands?
Where are they located?
Cats and pigs
On the carpus (on the back of the leg)
What species have Circumanal glands?
Dogs
What species have anal sac glands?
What do they do?
Cats and dogs
Used in marking, when animal poos they squeeze and empty them over the poo to communicate
What species have tail glands and where are they located?
Cats and dogs
On the top of the tail
What species have horn glands?
Give 2 considerations
Goats
- they are more productive in breeding season
- They are sometimes removed due to smell
What species have glands of the infraorbital pouch and where are they?
Sheep - near the eye
What species have glands of the interdigital pouch?
What are they used for?
Where are they located?
Sheep
Trail marking
Between the digits of the foot
What species have glands of the inguinal pouch?
What is the function?
Sheep
The odour may help lambs find the udder
What species have preputial glands?
Boars
What type of sweat do apocrine and endocrine glands secrete?
Apocrine = albuminous (protein rich) sweat
Eccrine = more watery sweat
Where do apocrine and eccrine sweat glands excrete their sweat?
Apocrine = into hair follciles to coat the hair
Eccrine = directly onto the skin
Where are apocrine and eccrine glands located?
Apocrine = over most of the body (haired skin) in domestic animals
Eccrine = generally only in certain areas (naked skin) e.g. footpads of dogs and the nasolabial plate of cattle
What produces an individuals odour?
Apocrine sweat secretion reacts with bacteria to produces an individuals odour.
Describe the secretion of apocrine sweat glands.
Apocrine sweat glands secrete via apocrine secretion.
They pinch off bits of cells to secrete packets of cell membrane and cytoplasm.
Describe the secretion of eccrine sweat glands.
Eccrine sweat glands secrete via merocrine secretion.
They secrete via exocytosis.
Vesicles form in the cells, and cell vesicles fuse with the membrane to discharge its contents and no part of the cell is lost so sweat is watery.
Although there is a distinction between apocrine and eccrine sweat gland secretion is this definitely correct? Why?
No, it may be wrong, they might actually both be merocrine.
What do apocrine and eccrine sweat glands look like on histology?
They look similar, they are both coiled tubular glands
What animals are mammary glands unique to?
mammals
Where have mammary glands evolved from?
They are extremely modified apocrine sweat glands
What are the 2 basic functions of mammary glands?
- secretion of milk which is rich in protein and fat for nourishing young
- It contains antibodies for immune transfer
What parts are mammary glands made up of?
A body (mamma) and teat
What are collections of mammary glands called in ruminants and horses?
udders
What are supernumerary teats?
Describe them and what we do about them
Extra buds on the teat, they can be independent or attached to more developed glands, they are mainly just a cosmetic problem and they are often removed in species used for milking - because they can be uncomfortable in the milking machine or may cause milk to go on the floor
Describe the distribution of mammary glands in: Sow Dog Cat Cow Sheep Horse
Sow = 14 teats, each with 2 openings Dog = 10 teats, each with many openings Cat = 8 teats, each with many openings Cow = 4 teats each with one opening Sheep = 2 teats each with one opening Horse = 2 teats each with 2 openings
Explain how milk is made and secreted
- Milk is produced by mammary epithelial cells that line the alveoli
- Alveoli are surrounded by smooth muscle cells called myoepithelial cells that push milk out of the alveolus into milk ducts
- Milk drains out through the milk ducts (it travels through the lobular ducts then through the lactiferous ducts) and into a lactiferous sinus
- Milk is then stored in the lactiferous sinus which is mostly in the teat (called the teat sinus) but part of it is in the body (called the gland sinus)
- A smooth muscle sphincter at the teat orifice prevents milk leakage and bacteria entry
- When stimulated milk is let down under the influence of hormones - because it causes contraction of myoepithelial cells around the alveoli and relaxation of the teat sphincter muscle
What is the milk let down reflex stimulated by?
Suckling. but it can be conditioned by the noise and routine of milking for cows
How many mammary glands, teats and teat orifices do cows have?
4 glands
4 teats
1 orifice per teat
In cows is there any milk duct crossover between the 4 quarters?
no
What is the relevance of a mucosal fold in the cow mammary gland?
What does the fold contain and why is this important?
The mucosal fold marks the transition between the gland sinus and teat sinus.
Containing a venous plexus so there is a risk of excessive blood loss if the teat needs amputating
When are cow mammary glands fully developed? Briefly describe development in life stages
At the height of lactation.
They are underdeveloped in juvenile males and females.
They start to develop in females at puberty
They are full size and function with pregnancy
What happens to mammary tissue between pregnancies?
It involutes/regresses but never quite regresses to the pre lactation size so increases in size with every pregnancy.
A keratin plug also forms during the non lactating period to prevent infection.
Describe the suspensory apparatus of the mammary gland of cows
The suspensory apparatus supports the mammary gland.
The median suspensory ligament is more elastic and runs through the middle.
The lateral suspensory ligaments are more fibrous and run down the dises.
Do birds have sweat glands?
No
How do birds lose heat?
Via the skin - from blood flow to lightly feathered areas
Via respiratory evaporation (panting)
What does the preen gland produce and what are the 4 functions of it?
An oily secretion.
For:
1. Waterproofing
2. Feather care
3. Has antimicrobial and antiparasite function
4. Is a vitamin D precursor to make vitamin D
Do reptiles have skin glands?
Yes - but not many
Name the 2 types of reptile skin glands, where they are and what species have them
- Scent glands at the vent - most lizards and snakes
- Pre-femoral glands/femoral pores = many lizards
Do ferrets have skin glands? What is the relevance?
No - so are at risk of hyperthermia.
Describe ferret sebaceous glands.
They are widely distributed in skin, they give the characteristic musky smell and the smell can be reduced by neutering.
Do ferrets have anal glands?
Yes
Do guinea pigs have sebaceous glands?
Yes
What is an important guinea pig sebaceous gland? Describe it
The caudal gland AKA grease gland.
It is influenced by hormones and is used for territory marking
Name the 2 skin glands in hamsters and gerbils and describe them
Flank scent glands - on the sides of the animal. May be wet, greasy and pigmented.
Ventral glands - can be greasy, protuberant and hairless
Name the 3 rabbit scant glands.
- Chin gland
- Inguinal glands
- Anal glands
Where are rabbit inguinal glands located?
Either side of the genital opening
Do fish have sebaceous or sweat glands?
No
What type of glands do fish have and what is the function?
Mucous glands for insulation and protection.
May also have poison glands (depending on species)
